1. Field of the Invention
The present invention relates to an apparatus for recording and reproducing optical information on and from an optical record medium such as optical card and optical disc, in which the optical information is recorded on the optical record medium, while the just recorded optical information is verified.
2. Related Art Statement
In the optical information recording and reproducing apparatus of the kind mentioned above, in order to verify the recording operation by a recording light beam, a verifying light beam is made incident upon the optical record medium in addition to the recording light beam and a verifying light receiving element is provided for receiving the verifying light beam reflected by the optical record medium. In an apparatus for recording and reproducing optical information on and from an optical card, the optical card is moved with respect to light spots in a reciprocal manner in a direction of a track on the optical card. Therefore, in order to perform the verifying operation during the forward movement as well as the backward movement of the optical card with respect to the recording light beam, two verifying light beams are made incident upon the optical card such that the recording light beam spot on the optical card situates at a middle point between the two verifying light beam spots viewed in the direction of the track on the optical card.
During the recording mode, a power of the recording light beam is changed from a lower reproducing level to a higher recording level, and the recording light beam having the higher power is reflected by the optical record medium and is made incident upon the verifying light receiving elements. In this manner, the verifying operation is affected by the leakage of the recording light beam and could not be carried out correctly. In order to remove such an influence of the leakage of the recording light beam reflected by the optical record medium onto the verifying light receiving elements, it has been proposed to produce a verify signal by deriving a difference between two output signals from the verifying light receiving elements. In the verify signal, the influences of the leakage of the recording light beam upon the two verifying light receiving elements are cancelled out.
Such an optical information recording and reproducing apparatus has been known from, for instance Japanese Patent Laid-open Publication Kokai Hei 8-255346. In this known optical information recording and reproducing apparatus, as illustrated in FIG. 1, a recording light beam and two verifying light beams are projected on an optical card 4 to form a recording light spot 92 and two verifying light spots 93a and 93b on a same track 91a of the optical card such that the recording light spot 92 situates at a middle position between the verifying light spots 93a and 93b. The optical card 4 is moved reciprocally in a direction of the track with respect to the light spots 92 and 93a, 93b, and the optical information is recorded on the optical card 91 by modulating the intensity of the recording light spot 92 in accordance with the optical information.
In FIG. 1, the optical card 1 is moved downward relative to the light spots 92 and 93a, 93b, so that the verifying light spot 93a is formed on a blank portion of the track 91a where no information has been recorded. When the optical card 4 is moved upward, then the verifying light spot 93b is made incident upon the blank portion of the track. The verifying light spots 93a and 93b are reflected by the optical card 91 and are made incident upon light receiving elements 94a and 94b as spots 95a and 95b, respectively as shown in FIG. 2. Output signals from the light receiving elements 94a and 94b are amplified by gain switching circuits (Gain SW) 96a and 96b, respectively. It should be noted that the verifying light beams are emitted from the same light source from which the recording light beam is emitted and are subjected to the modulation in accordance with a write signal to be recorded on the optical card. In order to compensate for such modulation in the verifying light beams, the gain of these circuits 96a and 96b is controlled or switched in accordance with the modulation of the recording light spot 92. Then, the amplified signals from the gain switching circuits 96a and 96b are supplied to a subtracting circuit 97 to derive a difference signal. This difference signal supplied from the subtracting circuit 97 provides a verify signal for verifying the information just recorded by the recording light spot 92.
In the known optical information recording and reproducing apparatus, the verifying light spots 93a and 93b are formed on the optical card 91 on opposite sides of the recording light spot 92 viewed in the direction of the information track 91a, the verifying light beams reflected by the optical card 91 are separately received by the light receiving elements 94a and 94b, and the difference between the output signals of these light receiving elements is derived to produce the verify signal. In this manner, signal components due to the leakage of the recording light spot 92 having a higher power onto the verifying light receiving elements 94a and 94b can be cancelled out.
In the known optical information recording and reproducing apparatus, when a defect 98 is existent on the track 91a of the optical card 91 as depicted in FIG. 1, the defect passes through the verifying light spots 93a and 93b at different time instances. That is to say, the defect 98 is first detected by the verifying light spot 93a, and then after a time interval during which the optical card 91 is moved over a distance between the verifying light spots 93a and 93b, the defect is detected again by the verifying light spot 93b. This is represented in FIGS. 3A-3D, in which FIG. 3A shows the write signal to be recorded on the optical card 91, FIGS. 3B and 3C represent the output signals of the gain switching circuits 96a and 96b, respectively, and FIG. 3D depicts the output signal of the subtracting circuit 97. The influence of the defect 98 appears in the output signals of the gain switching circuits 96a and 96b at different timings, and therefore the output signal, i.e. the verify signal includes the influence of the defect 98 twice and the verifying operation could not be performed correctly.
Moreover, as illustrated in FIG. 1, since the two verifying light spots 93a and 93b are positioned on opposite sides of the recording light spot 92 viewed in the track direction, the distance between the verifying light spots 93a and 93b is liable to be relatively larger. Therefore, if the recording light beam is reflected by the optical card in a non-uniform manner, the reflected recording light beam received by one of the verifying light receiving elements 94a and 94b becomes different from that received by the other of the elements 94a and 94b. This results in that the influence of the leakage of the recording light beam onto the verifying light receiving elements 94a and 94b could not be removed effectively.